There are various kinds of A-to-D converters (ADCs). Among others, successive approximation type ADCs have a good balance of accuracy, speed, cost, and the like and have been used in various applications. A successive approximation type ADC generally includes a capacitor array or resistor string D-to-A (digital-to-analog) converter (DAC), a successive approximation register (SAR), and a comparator, and converts an analog signal to a digital signal by binary search. The SAR successively determines a digital value from a most significant bit (MSB) based on an output value of the comparator. More specifically, the SAR sets a first lower bit from the successively determined bits to “1” and the DAC outputs an analog value corresponding to this digital value. When an input analog signal is larger than this analog value, the first lower bit is retained at “1.” Otherwise, the lower bit is set to “0.” The input analog signal is thus converted to an n-bit digital signal by n comparison operations (see, for example, Non-patent document 1). Non-patent document 1: Sagara, Iwao. A/D•D/A Henkan Kairo Nyumon (Introduction to A-to-D and D-to-A Converter Circuits). 2nd ed. The Nikkan Kogyo Shimbun, Ltd., March 2003. pp. 114-115.